A swath of borrowers are set to experience payment shock in 2014 as payments due on a crop of home equity lines of credit (HELOCs) made during the housing boom begin to rise abruptly, The New York Times reports.

For years, borrowers making monthly payments on about $30 billion in HELOCs have had to pay only interest on the loans, according to the Times. But this year, they must begin paying both principal and interest on them, the Times said.

That will push up monthly payments for many of those HELOC borrowers by hundreds of dollars, potentially sparking a wave of defaults. The risk of delinquencies resulting from HELOC payment resets could increase even further from 2015 to 2017, since even larger volumes of HELOCs are set to reset during that period.

“Do they realize they have a situation where their payments could triple?” Jeffrey C. Taylor, a partner at a mortgage services firm, told the Times. “Are we going to see people having challenges making those payments? As 2014 plays out, we’re going to start to hear more about all of this.”